Avoidance of resonance in the inflatable sport ball by limiting the critical ratio

ABSTRACT

A sport ball having an internal device such as an internal pump has a critical ratio that insures that rebound characteristics or coefficient of restitution of the ball, such as a basketball, will be acceptable for use. The invention also includes the method for evaluating design and/or quality control of a sport ball by measuring the internal vibration and determining the critical ratio of the sport ball.

RELATED APPLICATIONS

[0001] This application is a Continuation-in-Part of and claims thebenefit of U.S. patent application Serial No. 09/594,980, filed Jun. 15,2000. That application is a Continuation-in-Part of and claims thebenefit of U.S. patent application Ser. No. 09/478,225, filed Jan. 6,2000, and further claims the benefit of U.S. Provisional Application No.60/159,311, filed Oct. 14, 1999.

[0002] The applicant also claims priority based on a provisional U.S.patent application Ser. No. 60/252,443, filed Nov. 21, 2000 entitled“Avoidance of Resonance in the Inflatable Sport Ball by Limiting theCritical Ratio.”

FIELD OF THE INVENTION

[0003] The present invention relates to sport or game balls, preferablyinflatable sport balls, and more preferably, inflatable sport balls witha mechanism for inflating or adding pressure to the ball, or otherinternal device, inside the ball.

BACKGROUND OF THE INVENTION

[0004] The present invention relates to all inflatable sport ballsincluding those that contain pump mechanisms for inflating or addingpressure to the balls, or which contain another internal device withinthe ball. The mechanism for inflating or adding pressure to the ball ispreferably a pump. Examples of other internal devices, referred toherein as components, which may be self-contained in the sport ballsinclude, but are not limited to, a storage container, a flashlight, akey holder, a watch, and the like. In some cases, such balls have aninherent asymmetric construction. Even if a counterweight is positionedat a directly opposite portion of the ball from the pump mechanism orother component, the ball assembly still is asymmetric when consideredfrom other axes.

[0005] Conventional inflatable sport balls, such as basketball,footballs, soccer balls, volleyballs and playground balls, are inflatedthrough a traditional inflation valve using a separate inflation needlethat is inserted into a self-sealing inflation valve. A separate pump,such as a traditional bicycle pump, is connected to the inflation needleand the ball is inflated using the pump. The inflation needle is thenwithdrawn from the inflation valve that self-seals to maintain thepressure. This system works fine until the sport ball needs inflation ora pressure increase and a needle and/or pump are not readily available.

[0006] Internal vibration in a sport ball may adversely affect theperformance of the sport ball. For example, a basketball with vibrationproblems may not dribble or bounce consistently, and a soccer ball mayroll or travel inconsistently or away from the intended target whenkicked or thrown. If the sport ball is a sport ball with a selfcontained inflation mechanism, such as a pump, or other internal device,there is an increased potential for vibration problems due to the addedinternal component. One of the worst internal vibration problems is acondition called resonance. Resonance, as used herein, is when theimpact loading of an object, such as a ball, occurs in tune with theobject's natural frequency of vibration. The natural frequency of theball is the frequency that the ball oscillates at in the absence ofexternal forces. There is a need for a method to measure this vibrationand minimize it in the final product so that the consumer does notnotice the vibration. Examples of sport balls which may be affectedinclude, but are not limited to, any inflatable sport ball such as abasketball, volleyball, soccer ball, football, playground ball or otherinflated ball.

SUMMARY OF THE INVENTION

[0007] An object of the invention is to provide a sport ball having aninternal pump, wherein the ball exhibits the same degree of bounceconsistency when dropped repeatedly with various orientations as acorresponding sport ball that does not include an internal pump.

[0008] Another object of the invention is to provide a method ofmeasuring the bounce consistency of a sport ball.

[0009] The present invention is directed to a sport ball having aninternal device, whereby the sport ball having the internal deviceconforms to the same specifications as a corresponding sport ball thatdoes not contain an internal device. The invention achieves theabove-noted objectives and provides a method for measuring the internalvibration and determining the critical ratio of a sport ball, therebyenabling the design of a sport ball with internal device, wherein theball is suitable for use in competitive play.

[0010] One preferred form of the invention is a sport ball comprising aself-contained inflation mechanism, wherein said sport ball comprising aself-contained inflation mechanism has substantially the same reboundcharacteristics as a corresponding sport ball that does not comprise aself-contained inflation mechanism. The self-contained inflationmechanism preferably is a pump.

[0011] The sport ball preferably is hollow, but also can contain a foamor other material. The ball can be a regulation or youth sizebasketball, soccer ball, football, volley ball or playground ball. Theball preferably comprises a cover formed from a material selected fromthe group consisting of leather, synthetic leather, composites, rubbermaterials, and combinations thereof.

[0012] Methods of characterizing the rebound characteristics of the ballinclude, but are not limited to, coefficient of restitution (COR),rebound height, rebound consistency, and critical ratio. A basketballcomprising a self-contained inflation mechanism according to theinvention preferably has a coefficient of restitution range of0.750-0.813 when tested repeatedly at different ball orientations,combined with a difference between the maximum and minimum coefficientof restitution values of 0.051 or less. In another preferred form of theinvention, the difference between the maximum and minimum coefficient ofrestitution values is 0.036 or less. When described by rebound height, abasketball of the invention has a rebound height of 50-57 inches whendropped on a wooden floor from a height of 72 inches. The differencebetween the maximum and minimum rebound heights when the ball is droppedrepeatedly with different orientations is 5.5 inches or less and morepreferably 4 inches or less. In another preferred form of the invention,the basketball has a rebound height of 50-54 inches when dropped on awooden floor from a height of 72 inches.

[0013] In a preferred form of the invention, the sport ball having aself-contained inflation mechanism has a minimum critical ratio which issubstantially the same as the critical ratio of a corresponding sportball that does not comprise a self-contained inflation mechanism. Thecritical ratio is defined as the half period of component vibrationdivided by the duration of the ball's impact with the floor. Preferably,the critical ratio is 0.95 or greater.

[0014] Another form of the invention is a method of determining thecritical ratio of an inflated sport ball, comprising the steps of:

[0015] a) determining the duration of the ball's impact with the floor,

[0016] b) determining the half period of component vibration, andcalculating the critical ratio by dividing the half period of componentvibration, (b), by the duration of the ball's impact with the floor (a).

BRIEF DESCRIPTION OF THE DRAWING

[0017] The invention will be better understood by reference to theaccompanying drawings in which:

[0018]FIG. 1 shows a cross section of a portion of a sport ball with aself-contained piston and cylinder arrangement operable from outside theball for adding air pressure to the ball.

[0019]FIG. 2 is a side view of the pump shown in FIG. 1.

[0020]FIG. 3 is an isometric view of the cap for the pump of FIG. 1showing the configuration for locking and unlocking the pump piston.

[0021]FIG. 4 is a detailed cross-section view of a one-way valveassembly for use on the exit of the pump of FIG. 1.

[0022]FIG. 5 is a more detailed view of the duckbill valve in the FIG. 4assembly.

[0023]FIG. 6 is a diagrammatic view showing the critical ratio versusmaximum minus minimum rebound height for various basketball designs.

[0024]FIG. 7 is a graph of COR versus rebound height for a basketballaccording to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] In a preferred embodiment, the sport ball is an inflated sportball with a self contained inflation mechanism or other internal device.The interior of the sport ball may also be hollow or may contain afoamed material. The sport ball may be any sport ball, such as, but notlimited to, a basketball, a football, a soccer ball, a volleyball, or aplayground ball, and it is preferably a basketball with a self containedinflation mechanism or other internal device, more preferably abasketball with a self contained inflation mechanism such as a pump.

[0026] The invention will be better understood by first considering thestructure of a typical ball incorporating one embodiment of an inflationpump. Referring first to FIG. 1 of the drawings, a portion of a sportball 10 is illustrated incorporating one embodiment of an inflationpump. The ball 10 which is illustrated is a typical basketballconstruction comprising a carcass 15 having a rubber bladder 12 for airretention, a layer 14 composed of layers of nylon or polyester yarnwindings wrapped around the bladder 12 and an outer rubber layer 16. Fora laminated ball, an additional outer layer 18 of leather or a syntheticmaterial comprises panels that are applied by adhesive and set by coldmolding, or other process known in the art for adhering panels to theball. The windings are preferably randomly oriented and two or threelayers thick. The windings form a layer which cannot be expanded to anysignificant degree and which restricts the ball from expanding to anysignificant extent above its regulation size when inflated above itsnormal playing pressure. This layer for footballs, volleyballs andsoccer balls is referred to as a lining layer and is usually composed ofcotton or polyester cloth that is impregnated with a flexible binderresin such as vinyl or latex rubber.

[0027] Incorporated into the carcass of the ball of the invention duringthe formation is the rubber pump boot or housing 20 with a centralopening and with a flange 22 which is bonded to the bladder using arubber adhesive. The boot is located between the rubber bladder 12 andthe layer of windings 14. An aluminum molded plug is inserted into theboot opening during the molding and winding process to maintain theproper shape central opening and to allow the bladder to be inflatedduring the manufacturing process. The central opening through the boot20 in configured with a groove 24 to hold the flange 26 on the upper endof the pump cylinder 28. The cylinder can optionally be bonded to theboot using any suitable flexible adhesive (epoxy, urethane or other.)The pump boot or housing has a groove 25 which contributes to the bounceconsistency of the ball.

[0028] Located in the pump cylinder 28 is the pump piston 30 which isshown in FIGS. 1 and 2. The piston includes an annular groove 32 at thebottom end, which contains the spring 34 which forces the piston up inthe cylinder 28. Also, at the bottom end of the piston 30 is acircumferential O-ring groove 36 containing an O-ring 38. As seen inFIG. 1, this O-ring groove 36 is dimensioned such that the O-ring 38 canmove up and down in the groove 36. The O-ring is forced into theposition shown in FIG. 1 when the piston is pushed down. In thisposition, the O-ring seals between the cylinder wall and the upperflange 40 of the groove 36. When the piston 30 is forced up by thespring 34, the O-ring 38 moves to the bottom of the groove 36 whichopens up a by-pass around the O-ring through the recesses 42 so that theair can enter the cylinder 28 below the piston 30. Then, when the pistonis pushed down, the O-ring moves back up to the top of the groove andseals to force the air out through the cylinder exit nozzle 46.

[0029] At the upper end of the piston are the two flanges 48 whichcooperate with a cylinder cap 50 to hold the piston down in the cylinderand to release the piston for pumping. The cylinder cap 50 is fixed intothe top of the cylinder 28 and the piston 30 extends through the centerof the cylinder cap 50. The cap 50 is cemented into the cylinder 28.FIG. 3 shows an isometric view of the bottom of the cylinder cap 50 andillustrates the open areas 52 on opposite sides of the central openingthrough which the two flanges 48 on the piston can pass in the unlockedposition. In the locked position, the piston is pushed down and rotatedsuch that the two flanges 48 pass under the projections 54 and arerotated into the locking recesses 56. Attached to the upper end of thepiston 30 is a button or cap 58 that is designed to essentiallycompletely fill the hole in the carcass and to be flush with the surfaceof the ball. This button may be of any desired material such as casturethane or rubber. Mounted on the upper surface of the cylinder cap 50is pad 60 which is engaged by the button 58 when the piston is pusheddown against the spring force to lock or unlock the piston. The padprovides cushioning to the pump and should also be flexible to match thefeel of the rest of the ball. Its surface should be textured to increasegrip.

[0030]FIG. 1 of the drawings shows a pump exit nozzle 46 but does notshow the one-way valve that is attached to this exit. Shown in FIG. 4 isa one-way valve assembly 62 of the duckbill-type to be mounted in theexit nozzle 46. This assembly comprises an inlet end piece 64, an outletend piece 66 and an elastomeric duckbill valve 68 captured between thetwo end pieces. The end pieces 64 and 66 are preferably plastic, such asa polycarbonate, and may be ultrasonically welded together.

[0031] Although any desired one-way valve can be used on the exit nozzle46 and although duckbill valves are a common type of one-way valves, aspecific duckbill configuration is shown in FIG. 4 and in greater detailin FIG. 5. The duckbill structure 68 is formed of an elastomericsilicone material and is molded with a cylindrical barrel 70 having aflange 72. Inside of the barrel 70 is the duckbill 74 which has an upperinlet end 76 molded around the inside circumference into the barrel 70.The walls or sides 78 of the duckbill 74 then taper down to form thestraight-line lower end with the duckbill slit 80. The duckbillfunctions in the conventional manner where inlet air pressure forces theduckbill slit open to admit air while the air pressure inside of theball squeezes the duckbill slit closed to prevent the leakage of air.Such a duckbill structure is commercially available from Vemaylaboratories, Inc. of Yellow Springs, Ohio.

[0032] A pump assembly of the type described and illustrated in FIGS.1-5 is preferably made primarily from plastics such as polycarbonate orhigh impact polystyrene, most preferably from polycarbonate. Althoughthe assembly is small and light weight, perhaps only about 25 grams, itis desirable that a weight be added to the ball structure tocounterbalance the weight of the pump mechanism.

[0033] Other forms of the invention may utilize different pumpconstructions and the precise sequence of manufacturing steps may varyin various forms of the invention. Those skilled in the art willrecognize the substantial benefits including the economies ofconstruction inherent in allowing the pumping mechanism to be designedto accommodate the environmental considerations inherent in normal useof the sports ball and not the much harsher conditions that areencountered during the manufacturing process.

[0034] In the context of basketball performance testing, rebound heightis defined as the height the top of a basketball attains when droppedfrom 72 inches onto a wooden floor surface. (Although the description ofthe preferred embodiment is phrased in terms of a basketball, it will beunderstood that the invention has application to other sports balls,such as soccer balls, volleyballs, footballs and playground balls.) Therebound height can also be described in terms of a coefficient ofrestitution (COR). The mathematical relationship between rebound heightand coefficient of restitution is described below in example 1. In arebound test, the surface upon which the ball is dropped is designed tosimulate a regulation basketball-playing surface, and it is a two inchthick wooden piece securely attached to a foundation. The rebound heightcan vary for a particular ball when it is dropped on different spots onthe ball. A useful measure of rebound height variability is thedifference between the maximum rebound height and the minimum reboundheight. It is a desirable feature to have basketball rebound height asuniform as possible when the ball is dropped repetitively with differentorientations. Player testing shows that basketballs with maximum minusminimum rebound height of five and one half inches or more are difficultto play with and control and are difficult to dribble. The basketballswith maximum minus minimum rebound height of five inches or less areacceptable for play and show no obvious dribbling problem. Basketballswith maximum minus minimum rebound height of four inches or less arepreferred. Additionally, it has been found that a basketball generallymust rebound to a height of between fifty and fifty-six inches overallto be acceptable, although individual preferred rebound height may varyfrom player to player.

[0035] The act of bouncing a basketball, or other sport ball, on a flooris a dynamic event with impact loading, elastic deformation andvibration. In a perfect impact, the kinetic energy of motion is entirelyconverted into elastic deformation of a ball. The elastic deformation islike loading a spring or diving board; it deforms, then it springs back.After motion stops (i.e., when the ball is at its maximum deformation),the energy stored in the deformation is released and all of the energyis converted into rebound velocity. The rebound velocity provides theball enough energy to rise to the original drop height under perfectimpact conditions.

[0036] In reality, impact is not perfect. When components of thebasketball vibrate after impact, they rob some of kinetic energy of theimpact. This acts to store some of the energy in the form of localvibrations that cannot be recovered and are not converted into reboundvelocity. The end result is to reduce the rebound height. Typically, thelocation on the basketball with the minimum rebound height coincideswith the maximum vibration of the component. In contrast, the locationon the basketball with maximum rebound height corresponds to a minimumamount of component vibration. It is therefore required to map thesurface of the basketball such that rebound height is known for allpoints on the ball. Typical mapping of the entire surface of the ballwill require rebound testing on each panel of the ball at approximatelyfive points per panel. The panel that where the pump is located willhave additional points tested, generally at one-half to one inchincrements along the panel. Additionally, the two ends of the ball arealso tested. Each point is tested several times to find the maximum andminimum. The difference between maximum and minimum rebound height canthen be determined.

[0037] A “quick test” may be utilized once a full mapping scheme for aparticular product has been determined. This quick test utilizes thedata previously acquired when mapping the entire surface of the sportball, and then tests only those locations where the maximum and minimumpoints are expected. Although the quick test is not as accurate, it maybe utilized for quick decisions regarding the vibration and rebound of asport ball.

[0038] Two critical factors must be considered in the study of theimpact of a ball on a floor. The first factor is the nature of theimpact loading, and the second factor is the natural frequency of theball. The natural frequency of the ball is affected by the vibration ofthe internal device or component (i.e., a self contained inflationmechanism or other internal device) in the ball or part of the ball. Thenatural frequency of the ball with an internal component is measuredwith the internal device or component installed in the ball. As usedherein, the term natural frequency of the ball is the lowest vibrationfrequency of the ball with the internal device installed in the ball.The impact loading is the force acting on the ball to decelerate it to astop on the floor, backboard, rim, etc. and cause the ball to bounceback. The quantities of interest are the force and time history. Thenatural frequency of the ball influences how fast and to what extent theball will respond to the impact and how much of the impact energy willbe stored in local ball vibrations. The period of vibration is the timerequired to complete one cycle of motion. The period of vibration isequal to one divided by the frequency of vibration.

[0039] This invention includes a novel method to quickly analyze a sportball. This invention has particular application to a basketball,although the invention is not limited to such balls. The inventors havenow found that the ratio of two critical impact parameters are directlyrelated to the maximum minus minimum rebound height. The two criticalimpact parameters are the duration of the ball's impact with the floorand the half period of component vibration. The half period vibrationfor a basketball having a self-contained inflation device installed isequal to one half of the inverse of the natural frequency of theinstalled component. The critical ratio is most easily measured when theball, with the component installed, is dropped on the spot that yieldsthe minimum rebound height. As previously described herein, the minimumrebound height is found by mapping the surface of the ball. The “quicktest” may be used once a surface is mapped for the same constructionsport ball, but small changes to the component or the materials willrequire complete mapping to determine the proper locations that yieldmaximum and minimum rebound heights. As used herein, “critical ratio”refers to the half period of component vibration divided by the durationof the ball's impact with the floor. (Although this description is mostrelevant to a basketball and a pump, it will be understood that theinvention has application to other sport balls and other components,preferably other sport balls with a pump.)

[0040] The duration of the ball's impact with the floor can be measuredwith high speed digital imaging. It will be understood that the durationrefers to the duration of contact of the ball with the floor, and theduration of impact does not vary with drop location. The duration ofimpact should be measured at the location yielding the minimum reboundheight. The ball's impact with the floor is first captured with the highspeed digital imaging system. A frame sampling rate of about 9,000 to13,500 frames per second is preferably recommended. Analysis of the setof images will indicate the number of image frames that the ball is incontact with the floor. The duration of the impact event is simply thetotal number of frames that the ball is in contact with the floordivided by the frame sampling rate.

[0041] The half period of vibration of a basketball or other sport ballcan also be measured using high speed digital imaging. Analysis of theset of images allows the determination of the number of frames betweenthe maximum and the minimum length of vibration for a basketball havinga self-contained inflation device. The half period of vibration for abasketball having a self-contained inflation device is simply the totalnumber of frames between maximum and minimum vibration divided by theframe sampling rate. If the minimum vibration is difficult to estimate,an alternate method may be used to determine the half period ofcomponent vibration. Using the alternate method, the number of framesbetween one maximum and the next maximum limit of vibration isdetermined. In this method, the half period of component vibration isthe total number of frames between the two maximums divided by two, andthen divided by the frame sampling rate. Alternatively, the half periodof basketball vibration can also be determined by measuring the naturalfrequency directly with an accelerometer. As indicated above, the halfperiod of vibration is equal to one half of the inverse of thefrequency. Alternatively, dropping the ball onto a load cell andmeasuring the force over time may be used to measure the duration of theball's impact.

[0042]FIG. 6 illustrates test data for a plurality of basketballs. Foreach basketball, the maximum minus the minimum rebound height wasdetermined by mapping the surface of the basketball. Thereafter, thecritical ratio for each of these basketballs was determined by testing.Each point or dot in the diagrammatic view of FIG. 6 represents the testresults for a single basketball. These test results corroboratedecisively a strong negative correlation. More particularly, FIG. 6establishes that the maximum minus minimum height increases as thecritical ratio decreases.

[0043] In other words, the parameter that best correlates to maximumminus minimum rebound height for any specific basketball is the halfperiod of vibration for a basketball having a self-contained inflationdevice divided by the duration of the ball's impact with the floor. Thequotient of these numbers is referred to herein as the critical ratio.When this critical ratio is less than 0.95 for a regulation basketball,the maximum minus minimum rebound height is generally greater than fiveand one half inches, and the ball is therefore likely to be unacceptablefor play due to dribbling problems. When this critical ratio is greaterthan or equal to 0.95, the maximum minus minimum rebound height isgenerally less than or equal to five inches, and the ball is thereforesuitable for play. This critical ratio can be used in the design anddevelopment phase, as well as during quality control, to determine if aninflated ball will have rebound problems. If necessary, design changesmay be made to minimize the vibration before producing balls to be soldto customers.

[0044] Examples of the factors that affect the critical ratio include,but are not limited to, the stiffness modulus, flex modulus, bulkmodulus, tension modulus and compression modulus values of each of thecomponents of the ball, including the panels, carcass, bladder,windings, and boot; the inertia and mass of the pump or other internalcomponent, the local stiffness of the component's support, the airpressure in the ball, and the quality of the bond between thecomponent's housing (the “boot”) and the bladder and cover.

EXAMPLE 1

[0045] A regulation size synthetic leather basketball was made having adiameter of 9.43 inches (23.95 cm), a circumference of 29.5 inches (75cm), a weight of about 600 grams. The ball contained an integral pump ofthe type shown in FIGS. 1-5. The pump was configured to increase thepressure of the ball by at least 1 psi for every 200 pump strokes. Therebound of the ball when it was dropped from a height of 72″ (measuredfrom the bottom of the ball) onto a wooden surface designed to simulatethe floor of a basketball court was determined when the ball was droppedrepeatedly with different orientations. The ball was found to have arebound height in the range of 50-57 inches on all panels of the ball(measured from the top of the ball), with a difference between themaximum and minimum rebound heights of 5.5 inches or less. The lowestrebound height resulted when the portion of the ball surface that waslocated about 2 inches away from the pump was the part that contactedthe wooden surface.

EXAMPLE 2

[0046] The procedure of Example 1 was repeated with a differentbasketball of the same type, and the basketball was found to have arebound height in the range of 50-54 inches on all panels of the ball(measured from the top of the ball), with a difference between themaximum and minimum rebound heights of 4 inches or less.

EXAMPLE 3

[0047] The coefficient of restitution (COR) corresponding to variousrebound heights for the balls described in Examples 1 and 2 wasdetermined according to the following formula:

COR=V _(H) /V _(I)

[0048] wherein

[0049] V_(I) is the downward velocity of the ball upon initial impactwith the floor, and

[0050] V_(H) is the velocity of the ball as it travels upwardimmediately after impact with the floor.

[0051] Velocity for an object traveling vertically can be defined by theequation

v ²=2ax

[0052] Where v is velocity, a is acceleration due to gravity, x is thedistance to the floor from the initial drop point.${{More}\quad {specifically}},{V_{1} = \sqrt{2\left( {32.2\quad {{{ft}.}/s^{2}}} \right)\left( {12\quad {{in}/{ft}}} \right)\quad \left( {x\quad {in}} \right)}}$${{And}\quad V_{H}} = \sqrt{2\left( {32.2\quad {{ft}/s^{2}}} \right)\quad \left( {12\quad {{in}/{ft}}} \right)\quad \left( {h - {d\quad {in}}} \right)}$${{Stated}\quad {another}\quad {way}},{{V_{H}/V_{I}} = \frac{\sqrt{h - d}}{\sqrt{x}}}$

[0053] Wherein, h is the rebound height, and d is the ball diameter.

[0054] Furthermore, delta COR was determined by subtracting the CORcorresponding to the minimum rebound height of a particular ball fromthe COR corresponding to the maximum rebound height of the same ball.The calculated velocity, COR and delta COR results are shown below onTable 1. The data of Table 1 is plotted on FIG. 7, also shown below.Thus, a ball with a rebound of 50 inches has a COR of 0.7506, and a ballwith a rebound of 54 inches has a COR of 0.7868. The ball of Example 1was found to have a delta COR of 0.051. The ball of Example 2 was foundto have a delta COR of 0.036. Thus, for both of these balls, the maximumand minimum COR values for any single measurement were in the overallrange of 0.750-0.813. TABLE 1 COR for Basketball Rebound Height TestHeight Velocity COR (in) (in/sec) (n/a) Initial 72 235.88 — Rebound 40153.70 0.6516 41 156.20 0.6622 42 158.65 0.6726 43 161.07 0.6828 44163.45 0.6929 45 165.80 0.7029 46 168.11 0.7127 47 170.39 0.7224 48172.65 0.7319 49 174.87 0.7413 50 177.07 0.7506 51 179.24 0.7598 52181.38 0.7689 53 183.50 0.7779 54 185.59 0.7868 55 187.66 0.7956 56189.71 0.8042 57 191.73 0.8128 58 193.74 0.8213 59 195.72 0.8297 60197.69 0.8381 Min Max Delta COR (in) (in) (n/a) Rebound 50  55   0.0449Rebound 51  56   0.0444 Rebound 52  57   0.0439 Rebound 53  58   0.0434

[0055] The invention has been described with reference to the preferredembodiments. Modifications and alterations will occur to others uponreading and understanding the preceding detailed description. It isintended that the invention be construed as including all suchalterations and modifications insofar as they come within the scope ofthe claims and the equivalents thereof.

What is claimed:
 1. A sport ball comprising a self-contained inflationmechanism, wherein said sport ball comprising a self-contained inflationmechanism has substantially the same rebound characteristics as acorresponding sport ball that does not comprise a self-containedinflation mechanism.
 2. The sport ball of claim 1 , wherein the sportball is hollow.
 3. The sport ball of claim 1 , wherein the sport ball isa basketball.
 4. The sport ball of claim 3 , wherein the basketball is aregulation size basketball.
 5. The sport ball of claim 3 , wherein thebasketball is a non-regulation size basketball.
 6. The sport ball ofclaim 1 , wherein the basketball is a youth size basketball.
 7. Thesport ball of claim 1 , wherein the sport ball is a soccer ball.
 8. Thesport ball of claim 1 , wherein the sport ball comprises a cover whereinthe material is selected from the group consisting of leather, syntheticleather, composites, rubber materials and combinations thereof.
 9. Thesport ball of claim 1 , wherein the sport ball is a football, volleyball or playground ball.
 10. A sport ball according to claim 3 , whereinthe rebound characteristics of the ball comprise the rebound distance ofthe ball when dropped vertically from a height of 72 inches, and theball has a rebound of 50-57 inches.
 11. A sport ball according to claim10 , wherein the difference between the maximum and minimum reboundheights of the ball is 5.5 inches or less.
 12. A sport ball according toclaim 11 , wherein the ball has a coefficient of restitution of0.750-0.813.
 13. A sport ball according to claim 12 , wherein the deltaCOR of the ball is 0.051 or less.
 14. A sport ball according to claim 12, wherein the delta COR of the ball is 0.036 or less.
 15. A sport ballaccording to claim 3 , wherein the difference between the maximum CORand minimum COR of the ball when the ball is dropped repeatedly withdifferent orientations is 0.051 or less.
 16. A sport ball according toclaim 3 , wherein the difference between the maximum COR and minimum CORof the ball when the ball is dropped repeatedly with differentorientations is 0.036 or less.
 17. A sport ball according to claim 4 ,wherein the difference between the maximum COR and minimum COR of theball when the ball is dropped repeatedly with different orientations is0.051 or less.
 18. A sport ball according to claim 1 , wherein therebound characteristics of the ball comprise the rebound consistency ofthe ball.
 19. A sport ball according to claim 1 , wherein the reboundcharacteristics of the ball include the minimum critical ratio of theball, wherein the minimum critical ratio is equal to (half period ofcomponent vibration)/(duration of the ball's impact with the floor). 20.The sport ball of claim 1 , wherein the self-contained inflationmechanism is a pump.
 21. A sport ball having a self contained inflationmechanism and exhibiting a minimum critical ratio equal to: (half periodof component vibration)/(duration of the ball's impact with the floor),wherein the critical ratio is selected such that the sport ball havingthe self contained inflation mechanism exhibits substantially the sameminimum critical ratio as a comparable sport ball without a selfcontained inflation mechanism.
 22. The sport ball of claim 21 , whereinthe sport ball is a basketball.
 23. The sport ball of claim 21 , whereinthe sport ball is a soccer ball.
 24. The sport ball of claim 21 ,wherein the sport ball comprises a cover wherein the material isselected from the group consisting of leather, synthetic leather,composites, rubber materials and combinations thereof.
 25. The sportball of claim 21 , wherein the sport ball is a football, volley ball orplayground ball.
 26. The sport ball of claim 21 , wherein the selfcontained inflation mechanism is a pump.
 27. A method of determining thecritical ratio of an inflated sport ball, comprising the steps of: a)determining the duration of the ball's impact with the floor; b)determining the half period of component vibration; calculating thecritical ratio by dividing the half period of component vibration, (b),by the duration of the ball's impact with the floor, (a).
 28. A methodaccording to claim 27 , wherein the steps (a) and (b) are performedrepeatedly with different ball orientations.
 29. The method of claim 27, wherein the sport ball is a basketball.
 30. The method of claim 27 ,wherein the critical ratio is 0.95 or greater, and the basketball issuitable for play.
 31. The method of claim 27 , wherein the sport ballis a football, volley ball, soccer ball or playground ball.
 32. A sportball which comprises a self-contained inflation mechanism, the sportball having rebound characteristics determined by dropping the ballrepetitively with different orientations from a height of 72 inches ontoa wooden floor and measuring the rebound height that occurs whenrespective surface areas of the ball contact the floor, wherein the ballhas rebound characteristics according to which the maximum reboundheight minus the minimum rebound height is less than or equal to 5.5inches.